Turán numbers for suspensions of bipartite 2-regular graphs
For a graph $R$, let $\widehat R:=K_1+R$ denote its suspension, obtained by adding a new vertex adjacent to every vertex of $R$. For every fixed nonempty bipartite $2$-regular graph $R$, we determine $\operatorname{ex}(n,\widehat{R})$ for all sufficiently large $n$ and characterize all extremal graphs. Three distinct cases arise, according as $R$ is $2C_6$, a disjoint union of copies of $C_4$, or neither of these. This extends the known exact Turá results on odd wheels to suspensions of arbitrary bipartite 2-regular graphs.
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